1. Field of the Invention
The present invention relates to an ophthalmologic photocoagulator that conducts treatment on a diseased part of an eye to be examined by photocoagulation.
2. Description of the Related Art
Up to now, an ophthalmologic photocoagulator of a water cooling type, which is capable of continuously oscillating laser beam, has been a mainstream of the conventional ophthalmologic photocoagulator. Such an ophthalmologic photocoagulator is provided with a single laser oscillator, and uses treatment laser beam and sighting laser beam separately by inserting and removing a dense filter into and from an optical path of the laser beam. However, increase in the size of the conventional ophthalmologic photocoagulator is inevitable, causing a problem in view of spaces of a treatment room and an operating room. Note that the treatment laser beam means laser beam applied for conducting treatment on a diseased part of an eye to be examined by photocoagulation. In addition, the sighting laser beam means laser beam applied upon sighting for appropriately irradiating the diseased part with the treatment laser beam.
In view of the above-mentioned problem, a small-size ophthalmologic photocoagulators of an air cooling type that operates by power supplied through a general receptacle has been developed. Now, this type is the mainstream of ophthalmologic photocoagulators. In such an ophthalmologic photocoagulator, because laser continuous oscillation can not be made, a treatment laser oscillator that oscillates the treatment laser beam and a sighting laser oscillator that oscillates the sighting laser beam are separately provided. Here, in general, green laser beam having high energy is used as the treatment laser beam and red laser beam having low energy is used as the sighting laser beam. FIG. 3 is a schematic view showing a feature part of such an ophthalmologic photocoagulator 50.
The ophthalmologic photocoagulator 50 includes a treatment laser oscillator 51 that oscillates the green laser beam as the treatment laser beam, a sighting laser oscillator 52 that oscillates the red laser beam as the sighting laser beam, a dichroic mirror 53 for combining the optical path of the treatment laser beam with the optical path of the sighting laser beam, an optical fiber 54 composing a part of an optical system that guides laser beam to an eye to be examined, a condenser lens 55 that condenses laser beam to an incident end 54a of the optical fiber 54, and a photo diode 56 that receives a part of the treatment laser beam to monitor an output state of the treatment laser beam.
In the ophthalmologic photocoagulator 50, after sighting is focused on a diseased part on the eye fundus of the eye to be examined using the red sighting laser beam, photocoagulation on the diseased part can be conducted using the green treatment laser beam which is imaged onto the eye fundus through the same optical path as the sighting laser beam, without the treatment laser beam being deviated from the sighted portion. Accordingly, even in the small-size ophthalmologic photocoagulator in which the laser beam cannot be continuously oscillated, the same treatment as in the large-size ophthalmologic photocoagulator of water cooling type can be conducted.
In such an ophthalmologic photocoagulator, for example, a He—Ne laser is used as the sighting laser oscillator and an argon laser or a dye laser is used as the treatment laser oscillator. In addition, there have been known an ophthalmologic photocoagulator in which the wavelength of observation laser beam for observing the eye to be examined is different from the wavelength of the sighting laser beam, and an ophthalmologic photocoagulator in which the wavelength of the observation laser beam is equal to or different from the wavelength of the treatment laser beam. Note that, in such ophthalmologic photocoagulators, a dichroic mirror is used as a combining means for combining the optical path of the treatment laser beam with the optical path of the sighting laser beam (see, for example, JP 07-163613 A (paragraphs [0019], [0025], and [0026] and FIG. 1)).
However, the following problems are generated in the conventional ophthalmologic photocoagulators. That is, when the eye fundus having a color similar to the red sighting laser beam is spotted with the red sighting laser beam, the visibility thereof is bad. Therefore, it is difficult to conduct sighting on the diseased part with high precision. In addition, when the dichroic mirror is used as the combining means for combining the optical path of the treatment laser beam with the optical path of the sighting laser beam, a loss in the amount of any one of the laser beams that is transmitted through the combining means has to become large (about 7%).
Also, from a view point that the dichroic mirror has a characteristic in which a loss in the amount of light in the case of light reflection is smaller than that in the case of light transmission, it is necessary for the ophthalmologic photocoagulator disclosed in JP 07-163613 A to ensure efficiency to reduce the loss in the amount of light by using as the treatment laser beam for which a high output is required as the laser beam to be reflected. This becomes one of factors limiting the degree of freedom in design of an apparatus.